(In reply to re: Possible Solution
by Brian Smith)
My workings are long gone, but there is an additional note in my notebook that 3M + 4M = (3+4)(other factors) if M is odd, as it must be.
My concern at that point seems to have been eliminating a 7-free M as a divisor of the (other factors) hence the digression into Fermat.
Posted by broll
on 2017-06-24 23:37:45